Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$32.99	7.411%	$35.4349	$35.43	$35.45	$35.40
Purchase #2	$113.28	13.813%	$128.9274	$128.93	$128.95	$128.90
Purchase #3	$64.86	13.151%	$73.3897	$73.39	$73.40	$73.40
Purchase #4	$43.69	9.231%	$47.723	$47.72	$47.70	$47.70
Purchase #5	$46.37	11.344%	$51.6302	$51.63	$51.65	$51.60
Purchase #6	$191.49	7.183%	$205.2447	$205.24	$205.25	$205.20
Purchase #7	$83.44	7.749%	$89.9058	$89.91	$89.90	$89.90
7 purchase totals =	$576.12		$632.2557	$632.25	$632.30	$632.10